A non-aqueous electrolyte secondary battery, which contains olivine-type lithium complex compound particles for the positive electrode active material thereof, has recently been proposed for use as a battery expected to offer reduced size, lighter weight and higher capacity, and has been provided for practical use (see, for example, Patent Documents 1 and 2).
This non-aqueous electrolyte secondary battery is composed of a positive electrode, which uses a lithium-containing phosphoric acid compound having an olivine structure, a negative electrode, which uses a lithium-containing metal oxide having the property of being able to reversibly incorporate and release lithium ions of a carbon-based material and the like, and a non-aqueous electrolyte.
This positive electrode is formed by coating a positive electrode material mixture, which contains olivine-type lithium complex compound particles such as lithium iron phosphate (LiFePO4) particles, the surface of which is covered with a carbonaceous film, and a binder, onto the surface of a metal foil referred to as a current collector.
Since this type of non-aqueous electrolyte secondary battery is lighter, more compact and has higher energy in comparison with conventional secondary batteries such as lead batteries, nickel-cadmium batteries or nickel-hydrogen batteries, it is used as a power supply of portable electronic devices such as cell phones or laptop personal computers. In addition, non-aqueous electrolyte secondary batteries have recently been considered for use as high-output power supplies of electric vehicles, hybrid vehicles or power tools and the like, and these batteries used as high-output power supplies are required to have rapid charge/discharge properties.
In addition, non-aqueous electrolyte has been conventionally used in high output, high energy density secondary batteries, and secondary batteries are known that carry out charging and discharging by migration of lithium ions. In recent years, the use of olivine-type lithium-containing phosphoric acid salts such as lithium iron phosphate has been examined in order to improve stability at high temperatures (see, for example, Patent Document 3).